Cause:
With the latest release of Network Management Card 2 (NMC2) firmware AOS 5.1.1, with APPs SUMX/SY/SY3P 5.1.0, the NMC2 username can now be up to 64 bytes in length. (64 byte maximum supports up to 64 ASCII characters; Less for multi-byte languages OS). This was previously restricted to 10 characters and PowerChute Network Shutdown (PCNS) will still only be able to communicate with the NMC if the username is 10 characters or less. The PowerChute installers do not restrict the number of characters that a user can enter for the username nor do they provide any warnings about the max length.

Solution:
If the user configures the NMC2 username to be greater than 10 characters and does the same in PowerChute side, they will receive an error when trying to register with the NMC - "Security information did not match information at <IP Address>".